Senkbeil E, White H B
J Mol Evol. 1978 May 12;11(1):57-66. doi: 10.1007/BF01768025.
Lactate dehydrogenase and glycerol 3-phosphate dehydrogenase are metabolically coupled by the anaerobic dismutation of glyceraldehyde 3-phosphate and by the NAD redox state. This causes the concentrations of lactate and glycerol 3-phosphate to accumulate proportionally during anaerobic muscle contraction; these concentrations are high relative to those in aerobic tissues such as liver. We show that the isoenzymes of lactate dehydrogenase and glycerol 3-phosphate dehydrogenase from chicken breast muscle have Km values for lactate and glycerol 3-phosphate, respectively, that are 10-fold higher than the Km values measured for the lactate dehydrogenase and glycerol 3-phosphate dehydrogenase isoenzymes from chicken liver. The association of proportionally higher Km values with the potential for proportionally higher accumulation of substrates suggests that the isoenzymes of lactate dehydrogenase and glycerol 3-phosphate dehydrogenase from chicken muscle have evolved in parallel as a coupled metabolic unit distinct from the coupled isoenzymes in liver. The parallelism observed for the reduced substrates extends to the oxidized substrates, and to the coenzymes, NAD+ and NADH.
乳酸脱氢酶和3-磷酸甘油脱氢酶通过3-磷酸甘油醛的厌氧歧化作用以及NAD氧化还原状态在代谢上相互偶联。这导致在无氧肌肉收缩过程中,乳酸和3-磷酸甘油的浓度按比例积累;相对于肝脏等有氧组织中的浓度,这些浓度较高。我们发现,鸡胸肌中的乳酸脱氢酶和3-磷酸甘油脱氢酶同工酶对乳酸和3-磷酸甘油的Km值分别比从鸡肝中测得的乳酸脱氢酶和3-磷酸甘油脱氢酶同工酶的Km值高10倍。比例较高的Km值与底物比例较高的积累潜力相关联,这表明鸡肌肉中的乳酸脱氢酶和3-磷酸甘油脱氢酶同工酶作为一个与肝脏中偶联的同工酶不同的偶联代谢单元平行进化。观察到的还原底物的平行性延伸到氧化底物以及辅酶NAD⁺和NADH。